Checks files when opening project to see if they have been modified outside of DrJava. If a file has been modified, clears all of the bookmarks and breakpoints associated with that file.
Also fixed NullPointerException caused by bug [1651914] by adding a test for null.
M src/edu/rice/cs/drjava/model/AbstractGlobalModel.java
M src/edu/rice/cs/drjava/ui/InteractionsPane.java